Massive multi-input multi-output (MIMO) system received extensive attention in recent years. Researches show that massive MIMO system can significantly improve the spectrum efficiency along with the energy efficiency of a system by using linear detection and precoding algorithm such as zero-forcing algorithm and least mean square error. Thus massive MIMO system is likely to be adopted by the next generation communication standard as a key technology.
Existing reference signals for channel estimation include various types of reference signals adopted in Long Term Evolution Advanced (LTE-A)/Long Term Evolution (LTE) technology, such as channel state information RS (CSI-RS) and cell-specific reference signal (CRS) for estimating a physical channel coefficient and user equipment-specific RS (UE-RS) for estimating an effective channel coefficient.